I use theseā¦ the nylon hex bolt heads are ridiculously inexpensive, and the bolts have the ball socket holes that allow me/us to super level our modules from the top.
I simply use gel super glue to fix the nylon hex heads to the bolts.
The nylon bolt heads are easy on the surfaces, especially tablecloths.
The nylon bolt heads allow one to use a rachet wrench or fingers when pre-adjusting from the bottom